HEATING PRESS AND METHOD FOR VULCANIZING A VEHICLE TIRE IN THIS HEATING PRESS UNDER VACUUM

Description

[0001] The invention relates to a heating press for vulcanizing a vehicle tire, comprising a heating press upper part and a heating press lower part. A container comprising the molded parts of a vulcanizing mold and a cylindrical hood upper part enclosing the container are arranged on the heating press upper part. The heating press upper part and the heating press lower part are connected to the container in such a way that, when the heating press upper part is lowered by an axial stroke, the molded parts of the vulcanizing mold can be closed radially. The invention further relates to a method for vulcanizing a raw tire in this aforementioned heating press.

[0002] The heating press described above is a standard heating press for vulcanizing vehicle tires under atmospheric conditions.

[0003] The heating press comprises a container that houses the actual segmented vulcanizing mold, including the mold segments that give the tire its shape, sidewall shells, and bead rings. Heating chambers are also integrated for temperature control of the mold components. During vulcanization, the container is enclosed by a hood, which, in the prior art, primarily serves for temperature insulation during the vulcanization process.

[0004] To minimize defects on the tire surface, the air between the surface of the raw tire and the molding surface of the vulcanizing mold components must be removed. It is generally known that 1,000 to 5,000 vent valves are required in the mold components for this purpose. These vent valves allow air to escape radially and axially from the mold cavity through venting channels. However, the mold components of a new vulcanizing mold must be equipped with these valves. Furthermore, these valves tend to become clogged with rubber from the tire being vulcanized, necessitating time-consuming replacement or cleaning.

[0005] Patent specification US 5,145,688 A discloses a vulcanizing press with an upper and a lower part corresponding to the preamble of independent claim 1.

[0006] The invention is based on the objective of providing a heating press for vulcanizing a vehicle tire, with which vehicle tires can be reliably vulcanized in the vulcanizing mold without the need for venting valves. It is also an objective of the invention to provide a method for the time-efficient vulcanization of a vehicle tire using the aforementioned heating press.

[0007] The task is solved with regard to the heating press by The hood upper part is fixedly arranged on the heating press upper part; the hood upper part is dimensioned in its diameter such that it can be slid over the heating press lower part with minimal play and has a length sufficient to form a closed hood interior with the heating press lower part and heating press upper part when the vulcanizing mold is still open; at least one vacuum-tight seal is arranged on the surface where the hood upper part is slid over the heating press lower part when the hood interior is closed, in order to make the closed hood interior vacuum-tight, wherein the seal is preferably arranged on the heating press lower part; during a first stroke, the heating press upper part is movable in axial direction P1 such that the hood upper part forms a vacuum-tight hood interior with the heating press lower part.While the vulcanizing mold is still open to allow air in, a pump and a vacuum tank are arranged, by means of which a vacuum can be generated in the interior of the hood after the first stroke, wherein the vacuum tank and the pump are connected to the interior of the hood and wherein the vacuum tank and the pump are connected to each other, and wherein, during a second stroke, the upper part of the heating press can be moved further in the axial direction P1 such that the vulcanizing mold can be completely closed under vacuum conditions in the interior of the hood.

[0008] The key feature is that the heating press according to the invention vulcanizes vehicle tires under vacuum. The vulcanizing mold itself has no venting means for venting the mold cavity. Vacuum vulcanization eliminates the need for the 1000 to 5000 venting valves typically found in vulcanizing molds, which are used to radially expel air from the mold cavity. This eliminates the need for post-processing of the rubber protrusions on the tire caused by the venting means, as well as the replacement or cleaning of malfunctioning venting valves. This saves time and money. Furthermore, vacuum vulcanization gives the tire an external shape that is completely free of defects and therefore appears perfect.

[0009] The vacuum created within the closed hood after the first stroke of the heating press's upper section serves to remove air from the still-open vulcanizing mold, particularly between the outer surface of the tire and the forming surfaces of the mold's components. After the second stroke of the heating press's upper section, performed under vacuum conditions within the hood, the vulcanizing mold can be fully closed. The resulting tire can then be produced to a high standard and without defects.

[0010] It goes without saying that the hood or heating press may have additional seals to maintain a vacuum-tight interior. However, no modifications to the container or vulcanizing mold itself are to be made with regard to vacuum sealing measures.

[0011] The term vacuum refers to atmospheric pressure in the range of 950 mbar (abs) to 0.1 mbar (abs). It is advantageous if the seals are ring seals with round, square, and / or flat cross-sections.

[0012] For reliable sealing performance, it is advantageous to position the ring seal in a groove where the diameter of the ring seal is slightly larger than the depth of the groove. Slightly larger means that the seal, when installed in the groove and under seal, is compressed by a maximum of 40% compared to its compressionless geometry. Precise design of the groove in relation to the seal geometry further prevents damage to the seal and improves its durability.

[0013] In one embodiment of the invention, the ring seal consists of solid material. This solid material can consist of one or more materials known for seals, such as FKM or FFKM. These seals are cost-effective and easy to handle.

[0014] In another embodiment of the invention, the ring seal is a hose whose diameter can be changed. This has the advantage that the ring seal is subjected to less stress and its diameter is only increased when the sealing effect is required.

[0015] It is advantageous if the ring seal is a differentially pumped double ring seal. This has the advantage that any leaks can be compensated for with low pumping power.

[0016] It is advantageous for the vacuum tank to have a volume approximately 5 to 10 times larger than the volume of the closed hood (including mold, container, tire blank, and heating bellows). This ensures that a vacuum can be reliably generated within the hood. Furthermore, the time required to generate the necessary vacuum is significantly reduced. This can then take place during the normal loading and unloading process.

[0017] With regard to the method using the aforementioned heating press, the invention is solved by carrying out the following steps one after the other: a) Loading the open heating press by placing the raw tire to be vulcanized into the container. b) Moving the upper part of the heating press by a first stroke in the axial direction towards the lower part of the heating press until a closed hood interior is obtained, consisting of the upper hood, the upper part of the heating press, and the lower part of the heating press, while the vulcanizing mold is still open. c) Only if the ring seal is a hose with a variable diameter: Inflating the annular hose seal to create a vacuum-tight seal in the hood interior. d) Opening the connection between the vacuum tank and the hood interior to create a partial vacuum in the vacuum-tight sealed hood interior by pressure equalization between the vacuum tank and the hood interior. e) Upon maintaining the partial vacuum in the hood interior: Closing the connection between the vacuum tank and the hood interior.f) Opening the connection between the hood interior and the pump and pumping out the remaining air from the hood interior to create the vacuum; g) Moving the heating press upper part by a second stroke, moving the container so that the vulcanizing mold is completely closed, and subsequently closing the connection between the hood interior and the pump; h) Vulcanizing the raw tire and opening the connection between the pump and the vacuum tank and creating a vacuum in the vacuum tank, with the connection of the pump to the hood interior and the connection of the vacuum tank to the hood interior each being closed; h) Opening the heating press by moving the heating press upper part and unloading the fully vulcanized tire. and to vulcanize each additional tire, repeat steps a) - h).

[0018] To facilitate step h), it is advantageous to first open and then close another valve located in the hood to break the vacuum in the hood.

[0019] An exemplary embodiment of a heating press and the method for vacuum vulcanizing a vehicle tire, along with further advantages, are described with reference to the following two schematic figures. These show: Fig. 1 a heating press according to the invention with container in the open state, Fig. 2 the heating press of the Fig. 1 in the closed state.

[0020] The Fig. 1 Figure 1 shows a heating press 1 according to the invention with a container 2 in the open state. The tire blank can be inserted into the heating press 1.

[0021] The heating press 1 comprises a lower heating press part 6 and an upper heating press part 3 with a cylindrical hood 4 and has the corresponding mechanisms for positioning the tire to be vulcanized, for actuating the components of the vulcanization mold, for introducing the heating media, and for removing the finished vulcanized tire. Inside the hood 4, a container 2 is arranged on the upper heating press part 3 such that, when the upper heating press part 3 is moved in the axial direction P1, the mold components of the vulcanization mold arranged in the container 2 can be moved in the radial direction P2.

[0022] A central mechanism 8 is arranged, to which a heating bellows (not shown) is attached, which can be inserted into the tire blank (not shown). Nozzles (not shown) are also arranged on the central mechanism 8, through which a heating medium can be introduced into the heating bellows (not shown).

[0023] The cylindrical hood top part 4 is firmly mounted to the heating press top part 3 and has a length 23 which is sufficient to form a closed hood interior 12 with the heating press bottom part 6 and heating press top part 3 when the vulcanizing mold is still open, i.e. when the heating press top part 3 has not been completely moved onto the heating press bottom part 6.

[0024] The hood upper part 4 is airtight or vacuum-tight and, in the closed state, forms a vacuum-tight hood interior 12. To ensure a vacuum-tight seal of the hood upper part 4 in the closed state, a ring seal 5 is arranged on the heating press lower part 6 at the point where the hood upper part 4 passes over the heating press lower part 6 when the hood is closed. Further ring seals 9 provide a vacuum-tight seal at least between the central mechanism 8 and the hood interior 12.

[0025] Container 2 is a standard Container 2, already known in the prior art.

[0026] Container 2 contains the segmented vulcanizing mold with a lower heating plate 13, a lower side wall shell 14, an upper heating plate 15, an upper side wall shell 16, a lower bead ring 17, and an upper bead ring 18. The components of the vulcanizing mold that are moved vertically (= axially) (arrow P1) to open and close include the segment ring 19, consisting of seven to nine segment shoes 20 and the attached profile / mold segments 21, as well as the upper side wall shell 16 with the upper bead ring 18. The segment shoes 20 are moved apart radially, in the direction of arrow P2, to open and close the vulcanizing mold.A locking ring 22 is arranged on the upper heating plate 15. This locking ring has a chamfered inner surface that interacts with the chamfered outer surfaces of the segment shoes 20 of the segment ring 19 such that, when the vulcanization mold closes, the segment shoes 20 are drawn together radially towards the closed segment ring 19. Heating chambers are contained in the lower heating plate 13, the upper heating plate 15, and the locking ring 22. At least one heating medium, in particular saturated steam (water vapor), is introduced into these chambers for vulcanizing the tire. In this way, the raw tire (not shown) is heated externally via the segment shoes 20, the sidewall shells 14, 16, and the bead rings 17, 18. This heating process is commonly referred to as external heating.

[0027] A conventional heating bellows (not shown) is arranged in a known manner and filled under pressure with at least one heating medium to center the raw tire from the inside, thereby shaping the heating bellows into a tire-like torus form. Since the raw tire is heated from the inside via the heating bellows, this type of heating is referred to as internal heating.

[0028] During a first stroke H 1 - not shown in the figures - the hood upper part 3 can be moved in the axial direction P1 such that the lower area 7 of the hood upper part 4 moves over the heating press lower part 6 and forms a vacuum-tight hood interior 12 with it, while the vulcanizing mold is still open to allow air to pass through.

[0029] A pump 10 and a vacuum tank 11 are arranged, by means of which a vacuum can be generated in the interior of the hood 12 after the first stroke H 1. The vacuum tank 11 and the pump 10 are connected to the interior 12 of the hood, and the vacuum tank 11 and the pump 10 are connected to each other. Due to a vacuum in the interior of the hood 12, especially during the molding and vulcanization of the tire, the usual venting valves arranged in the mold surface of the vulcanizing mold are completely unnecessary.

[0030] The Fig. 2 shows the heating press 1 of the Fig. 1in a closed state, which is obtained after a second stroke H 2, in which the heating press upper part 3 can be moved further in the axial direction P1, so that the vulcanizing mold is completely closed under vacuum conditions inside the hood 12. The connection between the vacuum tank 11 and the hood interior 12 is closed. Subsequently, the connection between the hood interior 12 and the pump 10 is closed. The vulcanization of the raw tire then takes place.

[0031] Vulcanizing a passenger car tire takes approximately 15 minutes. During this time, the connection between pump 10 and vacuum tank 11 is opened to create a vacuum in the vacuum tank 11, while the connection between pump 10 and the hood, as well as the connection between vacuum tank 11 and the hood, remain closed. After the tire has been vulcanized, the volume of the hood interior 12 is vented via a valve (not shown), and the heating press 1 is opened to unload the fully vulcanized tire from the container 2, which contains the vulcanizing mold. For this purpose, the upper part 3 of the heating press, along with the container 2, moves upwards, and the tread segments 21 are simultaneously moved outwards in the radial direction P2. The tire is then released. Reference symbol list (Part of the description)

[0032] 1 Heating press 2 Container 3 Heating press upper part 4 Hood upper part 5 Ring seal 6 Heating press lower part 7 Lower area of ​​hood upper part 8 Center mechanism 9 Ring seal 10 Pump 11 Vacuum tank 12 Hood interior 13 Lower heating plate 14 Lower side wall shell 15 Upper heating plate 16 Upper side wall shell 17 Lower bead ring 18 Upper bead ring 19 Segment ring 20 Segment shoe 21 Profile segment / Form segment 22 Locking ring 23 Length of hood upper part P1 Axial direction P2 Radial direction H1 First stroke H2 Second stroke

Claims

1. Heating press (1) for vulcanizing a vehicle tire under a vacuum, - comprising a heating press upper part (3) and a heating press lower part (6), wherein a container (2) having the mold parts (14, 16, 17, 18, 21) of a vulcanizing mold and a cylindrical hood upper part (4) enclosing said container are arranged on the heating press upper part (3), and wherein the heating press upper part (3) and the heating press lower part (6) are connected to the container (2) in such a way that, when the heating press upper part (3) is being lowered through a stroke that takes place in the axial direction (P1), the mold parts (14, 16, 17, 18, 21) of the vulcanizing mold can be closed in the radial direction (P2), - wherein the hood upper part (4) is arranged fixedly on the heating press upper part (3), characterized in that - the diameter of the hood upper part (4) is dimensioned such that said hood upper part can be pushed over the heating press lower part (6) with a small clearance and said hood upper part has a length (23) which is sufficient to form a closed hood interior space (12) with the heating press lower part (6) and heating press upper part (4) when the vulcanizing mold is still open, - wherein at least one vacuum-tight seal (5) is arranged on that surface at which the hood upper part (4), when the hood interior space (12) is closed, is pushed over the heating press lower part (6), in order to make the closed hood interior space (12) sealable in a vacuum-tight manner, wherein the seal (5) is preferably arranged on the heating press lower part (6), - wherein, in the course of a first stroke (H1), the heating press upper part (3) can be moved in the axial direction (P1) in such a way that the hood upper part (4) forms a vacuum-tight hood interior space (12) with the heating press lower part (6), although the vulcanizing mold remains open in an air-permeable manner, - wherein a pump (10) and a vacuum tank (11), by means of which a vacuum can be generated in the interior space of the hood (12) after the first stroke (H1), are provided, wherein the vacuum tank (11) and the pump (10) are connected to the interior space (12) of the hood (4), and wherein the vacuum tank (11) and the pump (10) are connected to one another, and - wherein, in the course of a second stroke (H2), the heating press upper part (3) can be moved further in the axial direction (P1) in such a way that the vulcanizing mold can be completely closed under vacuum conditions in the interior space of the hood (12).

2. Heating press (1) according to Claim 1, characterized in that the seals are ring seals (5, 9) with circular, polygonal and / or flat cross sections.

3. Heating press (1) according to Claim 2, characterized in that the ring seal (5, 9) is arranged in a circular-ring-shaped groove, wherein the diameter of the ring seal (5, 9) is slightly greater than the depth of the groove.

4. Heating press (1) according to Claim 2 or 3, characterized in that the ring seal (5, 9) consists of solid material.

5. Heating press (1) according to Claim 2 or 3, characterized in that the ring seal (5, 9) is a hose of variable diameter.

6. Heating press (1) according to one or more of Claims 3 to 5, characterized in that the ring seal (5, 9) is a differentially inflated double ring seal.

7. Heating press (1) according to one or more of the preceding claims, characterized in that the vacuum tank (11) has a volume that is approximately 5 to 10 times greater than the volume of the closed hood (4).

8. Method for vulcanizing a pneumatic vehicle tire under a vacuum in a heating press (1) according to one or more of Claims 1 to 7, characterized in that the following steps are performed in succession: a) loading the opened heating press (1) by placing the green tire for vulcanization into the container (2), b) moving the heating press upper part (4) through a first stroke (H1) in the axial direction (P1) toward the heating press lower part (6), until a closed hood interior space (12) composed of hood upper part (4), heating press upper part (3) and heating press lower part (6) is obtained, while the vulcanizing mold remains open, c) only if the ring seal (5, 9) is a hose of variable diameter: inflating the circular-ring-shaped hose seal in order to seal off the hood interior space (12) in a vacuum-tight manner, d) opening the connection between the vacuum tank (11) and the hood interior space (12) in order to generate a partial vacuum, by way of pressure equalization between the vacuum tank (11) and the hood interior space (12), in the hood interior space (12) that has been closed in a vacuum-tight manner, e) when the partial vacuum is obtained in the hood interior space (12): closing the connection between the vacuum tank (11) and the hood interior space (12), opening the connection between the hood interior space (12) and the pump (10), and pumping the remaining air out of the hood interior space (12) in order to generate the vacuum, f) moving the heating press upper part (3) through a second stroke (H2), in the course of which the container (2) is moved in such a way that the vulcanizing mold is completely closed, and subsequently closing the connection between the hood interior space (12) and the pump (10), g) vulcanizing the green tire and opening the connection between the pump (10) and the vacuum tank (11) and generating a vacuum in the vacuum tank (11), wherein the connection of the pump (10) to the hood interior space (12) and the connection of the vacuum tank (11) to the hood interior space (12) are each closed, h) opening the heating press (1) by moving the heating press upper part (3) and removing the fully vulcanized tire, and repeating the steps a) - h) in order to vulcanize each further tire.

9. Method for vulcanizing a pneumatic vehicle tire according to Claim 8, characterized in that, to facilitate step h), this is preceded by a further valve arranged in the hood (4) being opened in order to deplete the vacuum and subsequently being closed again.